Process of recovering chemical from waste pulping liquor



Patented July 1, 1941 PROCESS OF RECOVERING CHEMICAL FROM WASTE PULPING LIQUOR Harold R. Murdock, Canton, N. 0., assignor to The Champion Paper and Fibre Company, Canton, N. C., a corporation of Ohio No Drawing. Application June 17, 1937,

Serial No. 148,815 A 3 Claims. (Cl. 92-2) This invention relates to an improvementin three commercial lay-products from an oil rethe recovery of pulping chemical from waste liqfinery: uor resulting from a chemical digestion of wood, and is concerned more particularly with the pro- Spent Spent Spent vision of make up chemical in the recovery of g g, 23 pulping values from waste liquor or the sulphate so, plant treater prcwaih process.

In recovering pulping values from the waste s eome mvity 1-159 1-092 1-069 l q 0f the ulphate (or kraft) process it is ig lz 12%; 12,1 3 conventional to concentrate the liquor, by evapneoezion'ioBiiiioibfiihieiiil Acid Basic Basic oration of much of its water content. to incing g g a i 1 erate the concentrated black liquor (usually, in Tota l s iifiu f- -glsf uji 76.2 6.70 5121 an oxidizing atmosphere) to smelt th re um i ikaii m mi 8s ent es- 1 12 32. 3 r g 103 blalck ash, in a reducing atmosphere, whereby to mm 4 W K yie d a melt containing sodium carbonate, so- 15 The above specific compositions r illustrative water, and to causticize the meltsolution by ad- :2 :5 a2?fifi z iiiiff fififfiinl iiiiiii fii lfirii ffitiiiii my my wide" i may be used directly for pulping more wood. process in which the original caust c sot afizgs In each such cycle of the pulping chemical employed gi gf s g n g considerable pulping chemical is lost or at least ng mgre en e o an not commonly recovered, and hence fresh chemi- It has been d that this by product material 23L25533122?$83di3 3?$ti$fi2 "i"' original quantity and strength" of the ul ing f i figgfig jfij fifi? 5 2:

liquor may be maintained. In the sulphate proct9 mcmera on u p y liquor has been concentrated and before the same 855 '2 1s conventwnal to use as h added chemi' is fed to the incinerator, and may with the solids 0& for t e make 9) salt lake Sodium content of said waste liquor, be incinerated and. sulphate, and to add such salt cake to the waste smelted, ielding additional pulping chemical material undergoing the recovery treatment at mainly in the form of sodium carbonate, sodium some point prior to the smelting step (e. g., to sulphide and some sodium sulphate. It the the black ash going to the smelter, or to the conr spent caustic contains a material amount 01 centrated liquor goin to the incinerator). The b s e ma i s (Organic. suc as e a make up of salt cake in the sulphate process may said hydrocarbonaceous residues,oreveninorganvary between, say, 200 pounds and, say, 500 10) those combustiblematerialsprovide apart or the pounds per ton of dry pulp produced, depending necessary fuel for the incineration thereby effectupon the care in operation, the types of equlp- 40 mg some economy in ,fueL m; employed, and other variables- If they spent caustic" is of such composition t has now been f d that a Spent caustic, that when added to the waste pulping liquor and by product from the treatment 01 on may be with the latter incinerated, smelted, leached and stituted for all or part of the salt cake convencausticizedi it would yield product which would tionally used as make up in the sulphate process, be deficient in sulphur, there maybe added to This spent caustic consists of or largely contains the f f spent caustic or to the waste sulphidic salts f sodium, g sodium sulphide, uor contaimng the latter an appropriate amount sodium polysulphide, sodium hydmsulpmde' of a suitable -SOr-containing material (e. 2., and/or other sodium salts of sulphur-containing sulphunc acid. as or preferably an on reacids, without or usually with hydrocarbonaceous finery sulphur acld sludge containing available residues or other organicmaterialsabstractedirom 40410119 whereby to increase the smpmcuty of the on, and results from one or another of the the chemicals content of the mixture red to the many processes for refining petrol u 011$ See incinerator. Provided the spent caustic contains chapter m, Chemical Refining of Petroleum, by residual free alkali the so added acid sludge serves Vladimir A Kanchevsky and Bert Allen Stagner, to neutralize some or all of the residual caustic published by The Chemical Catalog Company alkali or alkali carbonate of this by'rproduct Inc. New York 1933 spent caustic. Regardlessof whether or not the i i added acid sludge neutralizes the spent caustic,

T p l Wh t s meant by the xpression it does serve correspondingly to increase the ra- "spent caustic are the following compositions of tio of sulphur to sodium in the final product, and,

moreover, there is, of course, more than enough residual alkalinity in the black liquor to neutralize the added acid sludge in case the spent caustic does not do so. It is preferred to treat the spent incinerated, smelted, leached, and causticiz ed,

yielding a kraft cooking liquor in an amount sumcient for the production of 1 ton (dry basis) of or else directly to the incinerator contents by a.

feed separate from the waste liquor feed.

The following is given as an illustrative example I of one mode of carrying out the concept of the present invention:

In the production of 1 ton (dry basis) of kraft pulp from wood chips there was employed a pulping liquor containing per liter about 28.5 grams of NazS, about 0.5 gram of NazSO-r, about 60.8 grams of NaOH, and about 11.7 grams of NazCOs. In the cook an amount of this liquor was employed sufficient to represent a total of 1020 pounds of the pulping chemicals. It was determined that from the resulting waste pulping liquor there could be recovered only about 620 pounds, total, of pulping chemicals. .The waste liquor was concentrated, in knownmanner, to a concentration of about 30B. at 80 C.

To the concentrated waste liquor there were added 1685- pounds of an oil refinery by-product spent caustic which had been concentratedby evaporation and, at the'time added, was of the following constitution:

B. at 60 F deg 26.91 Sp. gravity; 1.2278 Sulphate ash (as Na2SO4) lb/cu. 'ft 18.22 Per cent Na2SO4 (sulphate ash) f per cent 23.77 Titratable NazO lb /cu. ft 4.20 Per cent titratable NazO per cent 5.48 Active NazO lb/cu. ft..- 0.05 Per cent active NazO 'per cent 1.3? Per cent water do 74.73 Per cent solids do 25.27

and the resulting mixture was in known manner kraft pulp.

The value sulphate ash of the above analysis is obtained by evaporating the spent caustic to dryness, adding sulphuric acid in an amount'at least suflicient to react with all of the base content of the evaporation residue, igniting the resulting product to a constant weight, and weighing the ignited product.

I claim:

1. In the process of recovering pulping chemical' from the waste pulping liquor of the sulphate process involving incineration of the solids content of such waste liquor and smelting of the,

incinerated solids, the step which consists in adding to such waste liquor, prior to actual incineration, a sulphurand sodium-containing byproduct spent caustic from the treatment of oil,

in an amount suflicient to make up the sodium content of the original pulping liquor. I

- 2. In the process of recovering pulping chemical from the waste pulping liquor of the sulphate process involving incineration of the solids content of such waste liquor andsmelting of the incinerated solids, the step which consists in adding to such waste liquor, prior to actual incineration, a sulphurand sodium-containing byproduct spent caustic from the treatment of oil, in an amount sufiicient to make up the sodium and sulphur contents of the original pulping liquor. v

3. In the process of recovering pulping chemical from the waste pulping liquor of the sulphate process involving incineration of the solids content of such waste liquor and smelting of the incinerated solids, the step which consists in adding to the waste liquors, after concentration of the latter and vafter the. concentrated waste liquors have been fed into the incinerator but prior to their actual incineration, a sulphurand sodium-containing by-product spent caustic from the treatment of oil, in an amount sufficient to make up the sodium and sulphur contents of the original pulping liquor.

4 HAROLD R. MURDOCK. 

